Dimethyl and phenyl silicones are useful lubricating fluids due to their heat stability and their low change in viscosity and volatility with temperature. However, these silicone fluids provide little lubricity to metal-to-metal interfaces and thus, their use is limited to the lubrication of metal-to-plastic interfaces, plastic-to-plastic interfaces and/or application operating under high speeds and light loads.
To improve the lubricity of dimethyl silicone fluids, inventors of U.S. Pat. No. 4,097,393 and U.S. Pat. No. 4,244,831 resorted to combining silicone fluid with hydrocarbon fluids, specifically naphthenic mineral oils, branched chain hydrocarbons, alkylated aromatic oils and synthetic poly alpha-olefins (PAO). However, neither patent taught the use of combinations of silicone fluids with synthetic or bio-based esters and/or alkoxylated aliphatic polyamine derivatives.
U.S. Pat. No. 7,399,734, teaches lubricating oil compositions comprising lubricating oil and a property-wear-improving amount of highly functionalized polymethylsiloxanes additives containing terminal or side chain residues derived from carboxylic acid esters, polyethers, thio groups and/or silanes. However, this patent does not address the problem of improving metal-to-metal lubrication of unfunctionalized dimethyl or phenyl silicone fluids.